When it comes to living on Mars, the human body is simply not suited to living for long periods in zero-g. Until this issue is solved, we have no hope of landing humans on the surface of Mars, nor can we create permanent residences in space. That was the crux of the testimony given to the House Committee on Science, Space, and Technology recently by best-selling author of The Martian, Andy Weir. “Astronauts who spend months in zero-g suffer bone loss and muscle degradation. Once they return to Earth, they have to be carried out of their capsule by ground crew. It takes days, sometimes weeks for them to re-adapt to gravity because their muscles are simply too weak to stand. Imagine, then, a crew of astronauts setting foot on the surface of Mars after eight months in space to get there. They would be unable to move, let alone execute their mission,” Weir said.